1. Field of the Invention
This invention relates to an internal combustion engine and, more particularly, to an internal combustion engine suitable especially for combustion of fuel mixtue having a lower fuel-air ratio.
2. Description of the Prior Art
Among the most reliable measures to reduce the amount of poisonous gases as produced during combustion of fuel in conventional internal combustion engines, there has been proposed a fuel combustion system wherein a fuel mixture having a lower fuel-air ratio is used. However, in conventional internal combustion engines, it is apparent that the lower the fuel-air ratio of the fuel mixture used is, the more difficult its combustion is. To solve this problem, a so-called stratified charge combustion system has been proposed in which fuel mixture is supplied to an internal combustion engine so that the concentration of fuel mixture in a layer about the igniter of the engine may be higher than that of fuel mixture in layers more remote from the igniter. However, for example, in certain engines embodying such a stratified charge combustion system and having a sub-combustion chamber for combustion of the higher density portion of stratified fuel mixture, an amount of polluting exhaust gas proportional to the volume of the sub-combustion chamber is necessarily generated. Therefore, this stratified charge system is not considered to be a complete unpolluting combustion system.
Furthermore, since conventional internal combustion engines adopt an intermittent expulsive combustion system wherein the propagating speed of combustion is very low, it will become more difficult to make synchronization with their piston as it is operated at a higher speed.
In addition, there have been proposed external combustion engines called "Stirling Engine" suitable for continuous combustion of fuel mixture as in steam engines. However, such stirling engines have the disadvantages that a special heat exchanging mechanism is required and that losses in exhausting and heat conducting are so high as to result in a low thermal efficiency.